It is desirable to control cloud formation and precipitation. Controlling cloud coverage by creating clouds or precipitating clouds provides some measure of control over warming, cooling, and climate benefits such as atmosphere albedo factors. Controlling precipitation has certain advantages, including helping farmlands to receive enough water to maximize crop output, aiding in the accumulation of natural snow on ski slopes, and helping to prevent precipitation when outdoor activities are scheduled.
Cloud formation requires both atmospheric water vapor and cloud condensation nuclei (CCN). Water vapor contained in the atmosphere condenses on the CCN when the atmosphere contains both the right amount of water and the right amount of nuclei. When water vapor condenses on the CCN in mass quantities, clouds form. When the particles of condensed water reach a critical weight, the condensed water droplets fall as precipitation.